Spark plug



June 1, 1943- R. F. LANDRUM 2,320,617

SPARK PLUG Filed May l2, 1941 ifs.

Rqginald E'Lndrum.

ATTORNEY Patented June 1, 1943 SPARK PLUG Reginald F. Landrum, Torrington, Conn., assignor of one-half to Eyvind Svendsen, Torrington,

Conn.

Application May 12, 1941, Serial No. 393,089

(Cl. 12S- 169) 'l Claims.

This invention relates to internal combustion engines and more particularly to an improved ventilated spark plug havingr a removable central electrode.

One object of this invention is to provide an improved spark plug of the above nature having an apertured top shell to ventilate the upper part of the central electrode to prevent overheating thereof.

Another object is to provide a spark plug of the above nature having means to completely insulate the metallic parts thereof to prevent accidental shocks to the mechanic when the spark plug is being installed or removed from the engine.

A still further object of this invention is to provide an improved spark plug of the above nature which will be relatively inexpensive to manufacture, simple in construction, compact,

ornamental in appearance, and very efficient and .la

durable in use.

With these and other objects in View, which will appear as the description proceeds, there has been illustrated in the accompanying drawing two forms in which the invention may be conveniently embodied in practice.

In the drawing:

Fig. 1 is a side view in elevation of a spark plug embodying the features and principles of this invention.

Fig. 2 is a top view of the same.

Fig. 3 is a vertical sectional view' of the same, taken on the line 3-3 of Fig. l, looking in the direction of the arrows.

Fig. l is an enlarged broken side View of the removable central electrode.

Fig. 5 is a longitudinal sectional view of a modilled form of connection for clamping the central electrode upon its seat in the insulating block.

Fig. 6 is a transverse sectional view of the same taken on the line 6-6 of Fig. 5 looking downwardly.

Referring now to the drawing, the numeral I indicates a metallic casing having a lower threaded shell portion II which is adapted to be screw-threaded into and grounded in the cylinder head of an internal combustion engine, not shown. The bottom of the casing I0 is provided with a pair of vertically spaced spark terminals I2 and I3 extending inwardly toward the central depending sparking terminal I4 of a centra-l main sparking electrode I5.

The central electrode I5 is adapted to be enclosed by a. hollow block I6 of porcelain or any other suitable insulating material, and said block is surrounded by the metal casing I0 which has an upper conical rim I'I spun inwardly around a top annular flange I8 of said block I6. The top of the casing ID is preferably made octagonal in shape whereby it may be manipulated by a wrench (not shown) to screw it tightly into the engine cylinder. The upper surface of the iiange I8 is provided with a raised neck Ilia which is flush with said rim portion I'I. The insulating block I8 is provided with a central stepped bore through which depends the main central electrode I5, said central bore of the block I6 comprising three stepped portions I9, 20, and 2l of diminishing diameter from top to bottom, thus forming a pair of upwardly directed shoulders 22 and 23. The top surface of the block I6 is counterbored and threaded, as at 24, whereby an upper shoulder 25 is formed. The block I5 has a conical bottom portion 25a surrounded by the lower end of the screw shell II.

The central main electrode I5 also decreases in diameter downwardly step-by-step to correspond with the stepped bore in the block I6, whereby three downwardly facing shoulders 2B, 21, and 28 are formed, each of which is undercut at 29 to provide a sharp depending annular rib 30 at the bottom of each shoulder. The electrode I5 has an upper threaded section 3I below which is an enlarged domed portion 32, said threaded section 3l being adapted to receive a metallic lock nut 33 and a grooved top metallic terminal nut 34, the threads of the section 3l serving to increase its heat radiating surface.

A polygonal dome-shaped electrode-clamping nut 35 is adapted to seat upon the upper domed surface of the enlarged electrode portion 32, said nut 35 having exterior screw threads to engage the interior thread of the counterbore 24 of said block I5. By means of this construction it will be seen that when the nut 35 is screwed downwardly into the counterbore 24, the sharp undercut ribs 30 of the electrode shoulders 26, 21, and 28 will be forced into three soft sealing washers 36, 3l, and 38 respectively which are disposed on the shoulders 25, 22, and 23 of the block I6, whereby the central electrode will be positively and effectively sealed in said block to prevent leakage of gases from the engine cylinder through the spark plug.

The upper threaded portion 3| of the electrode I5 is protected by a tubular Ventilating cover 39 of insulating material, such as porcelain, which is clamped downwardly upon the block I5 by the lock nut 33. The cover 39 is provided with a plurality of rows of outwardly directed downwardly-inclined holes 40 in its sides, whereby air will enter the same to cool the electrode I 5 when the engine is in operation. In order to protect the holes 40 fromrthe entrance of moisture, oil, dirt, etc., a series of annular deiiecting ribs 4l are provided on the exterior of the cover 39 directly over said rows of holes 4U. The upper part of the terminal top nut 34 is embedded in a surrounding knob 42 of insulating material, but the lower end of said nut 34 extends below said knob for detachable connection with the usual clip type conductor terminal leading to the distributor.

'Ihe conical upper rim of the casing Ill is provided with a plurality of radially disposed grooves 43 which... extend outwardly from the cover 39 to provide inclined drainage passages therefrom.

Operation In operation, the protective cover 39 may be l readily removed after rst unscrewing the knob 42 and its associated terminal nut 34 as well as the lock nut 33. The domed nut 35 may then be unscrewed, permitting the electrode l5 to be readily replaced with a new one.

One advantage of the present invention is that the provision of the perforated insulating cover 39 insures ythat the electrode l5 will not become overheated, and pre-ignition of the gases in the engine cylinder is thus avoided.

In the Imodified form of the invention shown in Figs. 5 and 6, an insulating block` 44 is disclosed which is provided with an undercut circular rim 45, having opposed radial slots 45, 4l extending outwardly from a central aperture 43. A domed clamping nut 49 similar to the nut 35 or" the first form, is located within the aperture 48 and said nut has vertical ilutings 5i! on its outer surface to facilitate the 'manipulation thereof. The nut 4i! is adapted to be screwed downwardly upon a screw shell 5l which has afbase flange 52 adapted to be located within the aperture 48--the edge of said flange E2 being provided with a pair of opposed outstanding lugs 53.

In the operation of the modified form of the invention, after the central electrode I5 has been inserted within the insulating block 44, the screw shell 5I will be arranged with its lugs 53 in alinement with the slots 46, 4l, pushed downwardly through the aperture 48, and then turned through a right angle to lock the screw shell lugs 53 under the rim 45. The nut 49 will then be pushed down over the threaded post 3l and screwed home upon the Vscrew shell 5I forcing the central electrode i5 tightly upon its seats 26, 21, 28, in the insulating block 44.

While there has been disclosed in this specification two forms in which the invention may be embodied, it is tobe understood that these forms are Ishown for the purpose of illustration only, and that the invention is not to loe-limited to the specific disclosures, but may be modified and embodied in various other forms without departing from its spirit. In short, the invention includes all the modifications and embodiments coming within the scope of the following claims;

Having thus fully described the invention, what is claimed as new and for which it is desired to obtain Letters Patent is 1.

l. In a spark plug, a removable main electrode having a plurality of stepped sections provided with undercut shoulders on their lower ends, an insulating block surrounding saidY electrode and having a plurality of steppedlbQres provided with seats for said shoulders, leakproof washers on said seats, and means to urge said electrode downwardly with respect to said block to clamp said undercut shoulders thereof upon said washers.

2. In a rspark plug, a central tapered removable main electrode having a plurality of stepped sections terminating in bottom downwardly directed shoulders and having an enlarged intermediate dome section, a hollow insulating block surrounding said electrode and having upwardly directed seats for said shoulders, a nut secured to said block and engaging said enlarged dome section to press said electrode downwardly to clamp the shoulders thereof upon said seats whereby leakage of gases from the engine cylinder is prevented.

3. In a spark plug, a main Iremovable electrode having a plurality of sections of diminishing diameter from top to bottom, the bottoms of said sections being provided with undercut shoulders, a hollow insulating block surrounding said electrode and having seats for said shoulders, and aV nut screwed to said block engaging said electrode to urge it downwardly. to clamp the shoulders thereof upon the seats in said block, whereby said spark plug is made gastight.

4. In a spark plug, a hollow insulating block, a central removable electrode seated in said block and extending downwardly therethrough into the ignition space of an engine cylinder, said block having an undercut upper recess` surrounding said electrode defining a rim, said rim having a radial slot, a collar, member surrounding said electrode and having a radial lug adapted to be passed downwardly through said slot and then be twisted out of alinement therewith to lock said lug under said rim, and a nut havingr interlocking engagement with said electrode for screwing upon said collar member and forcing sai-d electrode upon its seat in sai-d insulatingr block.

5. In a spark plug for insertion into the cylinder oi an internal combustion engine, an insulating block having a central bore provided with a plurality of stepped seats, an electrode having leak-proof engagement with said bore and having an intermediate enlarged dome and a plurality of stepped shoulders below said dome for engaging said seats, said block having a threaded counterbore in its upper end', anut screwed into said counterbore and engaging said dome to force said electrode downwardly to clamp said shoulders against said'seats, whereby said spark plug will be rendered gastight.

6. In a spark plug for insertion into the cylinder of an internal combustion engine, an insulating block having a central bore for receiving a sparking.electrode,y a tubular apertured ventilating fcover for embracing the upper part of said electrode, a screw shell located `beneath said cover for embracing said block, said shell having a plurality of `downwardly inclined. radial grooves in its upper exterior surface to provide drainage from said Ventilating cover.

'7. In a spark plug, a hollowinsulating block, a removable electrode located in Vsaid block and having an upper portion extending. above said block, and a tubular Ventilating cover surrounding and spaced from said upper portion to provide a substantial air space therebetween, said cover having a row of holes to provide ventilation for said electrode, and an annularjY outstanding rib on said cover above said Vro-w` ofiholestoexcludeY dust, moisture, oil,.etc., therefrom.

` REGINALDf LANDRM. Y 

